Since crystalline 1-butene polymers have excellent creep characteristics at high temperature, strength against deformation, and abrasion resistance, work has been done positively to develop their uses as water supply pipes, slurry transporting pipes, linings for steel pipes for slurry transportation, etc. It is known that when a crystalline 1-butene polymer such as poly-1-butene is solidified from its molten state, it first becomes pseudostable II-type crystals, and subsequently, transition to stable I-type crystals takes place slowly over several days [Journal of Polymer Science: Part A, Volume 1, Pages 59-84 (1963)].
However, the speed of crystallization of the crystalline 1-butene polymer to II-type crystals and the speed of transition from the II-type crystals to the I-type crystals are not sufficiently high, and moreover, the crystalline 1-butene polymer in the state of II-type crystals is soft. Accordingly, if shaped articles of the crystalline 1-butene polymer after melt-shaping undergo deformation during conveyance, transportation, storage, etc., and their crystal transition to I-type crystals occurs, the deformation remains in the shaped articles, and the value of the shaped articles as products is reduced. Much care and expertise are required, therefore, in handling the shaped articles before their crystal transition is over. In the field of melt-shaping of the crystalline 1-butene polymer, it is strongly desired to develop a 1-butene polymer composition whose speed of crystallization to II-type crystals and speed of transition from the II-type crystals to the I-type crystals is high.
The present inventors recognized that the conventional crystalline 1-butene polymers have the aforesaid defects in melt shaping, and studied the development of a crystalline 1-butene polymer composition whose speed of crystallization to II-type crystals and speed of transition from the II-type crystals to the I-type crystals is high. Consequently, they have found that the aforesaid defects are eliminated by a composition comprising a crystalline 1-butene polymer and a crystalline olefinic polymer having specific properties. The above discovery has led to the present invention.